NYPD says 19-year-old Tayari McClellan is under arrest and charged with assault and harassment.
Two other suspects remain on the loose.
The 25-year-old victim stepped in to stand up for that woman, he suddenly found himself under attack.
Eyewitness News spoke to the victim last week, who asked to have his identity hidden.
"They're punching me, kicking me, there were three people there. Crazy situation, I couldn't take them on myself," the victim said.
And while the 25-year-old man tried to fight his way out of the sudden attack, another passenger aimed a cell phone camera
"My jaw was hurt, black eye, nose hurts, makes a clicking sound," the victim said.
And what also hurts, he says, is that no one, not one passenger aboard the L train, came to his aid.
"At least do something to help, they laughed, like this is entertainment. How can they be laughing at such brutality," the victim said.
He first hoped the attackers would be thrown in jail.
Now, he thinks that instead of potentially learning more cruelty, what they really need is a lesson in kindness.
"A lot better if they were made to help the community, learn that there's a better way to living than the way they're living right now," the victim said.
He's talking to the police, and his own mother is offering a $1,000 reward for information leading to an arrest.